Rotary nozzles have been used widely with ladles for receiving molten steel tapped from a converter to transport the molten steel or pour it into molds, tundishes for receiving the molten steel from a ladle to pour the molten steel into molds, and the like.
For instance, FIG. 10 is a perspective view of a rotary nozzle of the type which has been in wide use and FIG. 11 is a schematic view showing its principal parts in section. In these figures, numeral 4 designates a base member attached to the bottom shell of a ladle 1 or the like, and 5 a support frame pivotably attached to the base member 4 with a hinge and formed with a recess 6 in which fixedly mounted is a fixed plate brick 7 made of a refractory material, having a nozzle bore 8. Note that numeral 2 designates a top nozzle fitted in the bottom shell of the ladle 1 or the like and a nozzle bore 3 of the top nozzle is adapted to be in alignment with the nozzle bore 8 of the fixed plate brick 7. Numeral 12 designates a rotor equipped with a gear 13 on the outer periphery thereof and formed with a recess 14 in which fixedly mounted is a slide plate brick 17 made of a refractory material, having nozzle bores 18, 19, and the rotor 12 being received in a case 28 which is pivotably attached to the base member 4 through a hinge. When the support frame 5 and the case 28 are closed, the slide plate brick 17 is pressed against the fixed plate brake 7 by a large number of springs 29 provided in the case 28. It is to be noted that numerals 24 and 25 designate bottom nozzles respectively having nozzle bores 26 and 27 which are respectively aligned with the nozzle bores 18 and 19 of the slide plate brick 17.
As shown in FIG. 12, the slide plate brick 17 is formed into a planar elliptic shape having flat portions 20a and 20b formed in parallel at the opposed portions thereof. On the other hand, the recess 14 of the rotor 12 is formed into a shape which is similar to and slightly greater than the slide plate brick 17 and whose sides are formed with locking portions 15 in correspondence to the flat portions 20a and 20b; and one of the locking portions 15 is formed with a cutout 16. Then, the slide plate brick 17 is received in the recess 14 of the rotor 12 and it is fixedly mounted in the recess 14 by fastening a wedge 22 fitted in the cutout 16 of the rotor 12 with a bolt 23.
The fixed plate brick 7 is also formed into substantially the same shape as the slidable plate brick 17 so that it is received in the recess 6 formed in the support frame 5 and it is fixedly mounted in the recess 6 by fastening screws 9 through locking members 10.
As will be seen from FIG. 10, the rotary nozzle constructed as described above is so designed that after the support frame 5 and the case 28 have been closed, the rotor 12 is rotated by an electric motor 30 through an intermediate gear 31 and the gear 13. Consequently the slide plate brick 17 mounted in the rotor 12 is rotated to optionally adjust the relative position of the nozzle bore 8 of the fixed plate brick 7 to the nozzle bore 18 (or 19) of the slide plate brick 17, and the degree of opening cooperatively defined thereby. It is to be noted that in addition to the previously mentioned elliptic shape, the fixed plate brick 7 and the slide plate 17 may also have a regular octagonal shape as shown in FIG. 13 (Patent Publication No. 4-11298).
While the rotary nozzle of the above-mentioned type is now in wide use because of its various merits over the reciprocating-type slide nozzles, the fixed plate brick and the slide plate brick, forming its principal parts, involve the following problems. That is to say, since the fixed plate brick and the slide plate brick, particularly at the nozzle bores and their surroundings are subject to the danger of producing erosion because of the passage of high temperature molten steel or the like which erosion causes the molten steel or the like to leak, the fixed and slide plate bricks have to be changed for every several charges and thus must be handled as consumable parts. However, as these fixed plate bricks and slide plate bricks are made of expensive refractory material, their cost is high, thus minimizing any possible reduction in cost.